one-true-awk: import 20210221 (1e4bc42c53a1) which fixes a number of bugs

Import the latest bsd-features branch of the one-true-awk upstream:

o Move to bison for $YACC
o Set close-on-exec flag for file and pipe redirects that aren't std*
o lots of little fixes to modernize ocde base
o free sval member before setting it
o fix a bug where a{0,3} could match aaaa
o pull in systime and strftime from NetBSD awk
o pull in fixes from {Net,Free,Open}BSD
o add BSD extensions and, or, xor, compl, lsheift, rshift

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